Re: [RFC PATCH bpf-next v3 2/2] selftests/bpf: add tests for selective kmod BTF loading

[Fuyu Zhao]

On 8/21/2026 8:10 AM, Eduard Zingerman wrote:
> On Wed, 2026-08-19 at 17:04 +0800, Fuyu Zhao wrote:
> 
> ...
> 
>> +++ b/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c
>> @@ -0,0 +1,196 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <test_progs.h>
>> +#include "kmod_btfs.skel.h"
>> +
>> +static bool btf_skipped;
>> +static bool dup_ignored;
>> +
>> +static const char btf_skip_fmt[] =
>> +	"libbpf: skipping module BTF '%s', not in kmod_btf_names\n";
>> +static const char dup_ignore_fmt[] =
>> +	"libbpf: duplicate kmod BTF name '%s' ignored\n";
>> +
>> +static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt,
>> +			   va_list args)
>> +{
>> +	if (!strcmp(fmt, btf_skip_fmt)) {
>> +		if (!strcmp(va_arg(args, char *), "bpf_test_no_cfi"))
>> +			btf_skipped = true;
>> +	} else if (!strcmp(fmt, dup_ignore_fmt)) {
>> +		if (!strcmp(va_arg(args, char *), "bpf_testmod"))
>> +			dup_ignored = true;
>> +	}
>> +
>> +	return 0;
>> +}
> 
> Idk what Andrii would say about this, but I'd rather add an internal
> function akin to:
> 
>   size_t bpf_object_btf_module_cnt(const struct bpf_object *obj);
> 
> in libbpf.c and expose it via libbpf_internal.h (*not* via API),
> instead of intercepting log messages.
> 
> ...

I think your suggestion is better. It also addresses the issue raised by
the bot about potentially hiding other libbpf logs. I'll wait for Andrii's
feedback on this.

Thanks,
Fuyu